function  plot_special_point(aisdata,point)
%UNTITLED2 此处显示有关此函数的摘要
%  在海图上绘制某些特定点
figure
DrawENC(aisdata, 'Original AIS Trajectory');
hold on
plot(point(:,1),point(:,2),'ro');
legend('船舶轨迹','轨迹急转点');
end